Electric power-generating system



July 22, 1930. F. w. GAY 1,111,252

ELECTRIC POWER GENERATING SYSTEM Filed Aug. 31, 192B A TTORNEY.

Patented July 22, 1930 PATENT OFFICE FRAZER W- GAY, OF NEWARK, NEW JERSEY ELECTRIC POWER-GENERATING SYSTEM Application filed August 31, 1928. Serial No. 303,145.

This invention relates, generally, to electric power generating systems and the invention has reference, more particularly to an electric power generating system wherein r a single source of power generation is adapted to supply two electrical circuits with electrical energy such that, though the voltage on one of said circuits may vary within wide limits, the voltage on the other of said circuits shall remain substantially constant under all operating conditions.

In modern central power stations the size of the individual generating units is so great that each unit is coming to be considered practically as a separate and independent power station. Each generator has its own turbines, boilers, auxiliary power supply and etc., separatefrom every other such unit. It is therefore required that such a generator provide its auxiliary apparatus with a source of power having a substantially constant voltage under all operating conditions, from no load on the generator circuits to short circuit thereof. Heretofore it has been customary to supply such auxiliary apparatus with power from a small generator direct coupled to the main generator shaft or from a small auxiliary generator driven by a small separate turbine. a

It is the object of this invention to provide a novel generating system wherein the main generator itself is adapted to supply not only the main load circuit but is also adapted to supply the auxiliary load circuit,

said auxiliary load circuit operating on a substantially constant voltage at all times and being substantially independent of volt age fluctuations in said main load circuit.v

More particularly this invention has for its object to providea generator having auxiliary windings which are normally adapted to supply electrical energy at a voltage in excess of the voltage impressed on said auxiliary circuit. Transition means are provided for converting a portion ofthis energy to the main load circuit under normal operating conditions and the remainder at a lower potential is used to supply the auxiliary loadcircuit. In the event of a short on circuit in the main load circuit, causinga c The generator 1 has auxiliary drop in the voltage generated in the generator windings, the transition means is adapted to pass the energy from the anxiliary windings onto the auxiliary load circuit with but little drop in voltage so that the voltage of the auxihary circuit remains substantially constant at all times.

Other objects of this invention, not at this time moreparticularly enumerated, will be clearly understood from the following detailed description of the same.

With the various objects of the invention in view, the same consists, primarily, in the novel construction and arrangement of gencrating system hereinafter set forth; and, the invention consists, furthermore, in the novel arrangements and combinations of the various devices and parts, as well as in the details of the construction of the same, all of which will be hereinafter more fully described and then finally embodied in the claims appended hereto.

The invention is clearly illustrated in accompanying drawings, in which Figure 1 is a diagrammatic representation of the novel power generating system of this lnventlon.

Figure 2 is a diagrammatic illustration of the operation of a portion of the novel power generating system of Figure 1. 8

Figure 3 is a diagrammatic representation of a slightly modified arrangement of generating system. I

Figure 4 is a view similar to Figure 1 but illustrates a standard three phase generator utilized as the energy source.

Similar characters of reference are employed in all of the hereinabove described views, to indicate corresponding parts. i

Referring now to the said drawings, the reference character 1 designates a three phase generator having main windings 2, 3 and 4 that are connected by leads 9, 13 and, 20 through suitable reactances 5, (Sand 7 respectively, and through" a circuit breaker'8 toa three phase main power bus 10, 11 and 12.

' wer windings 14, 15 and 16, each of which windings are preferably ositioned centrally with respect to one of t e main winding's 2, 3 and 4;

the

-' line 21, 22

Thus, assuming the enerator 1 to be wound with seven coils per pole per phase, the mid coil of each phase may be used as one of the windings 1 1, and 16 while the remaining six coils of each phase would constitute one of the main windings 2, 3 and 1. As thus connected, the time phase of the generated E. M. F. of any one of the windings 1 1, 15 and 16 is the same as the average time phase of the corresponding adjacent winding 2, 3 or 41. The windings 14, 15 and 16 are connected by leads 14, 15 and 16 to one of the secondaries 17, 18 and 19 respectively of a bucking transformer bank 24. The other end of the secondaries 17, 18 and 19 are connected in turn to the loads 21, 22 and 2-3 of an auxiliary power circuit. his auxiliary power circuit is adapted to supply electrical energy to the auxiliaries such as pumps, blowers, etc. of the generator 1. The primaries 26, 27 and 28 of the transformer bank 241 are each connected at one of their ends to the leads 9, 13. and respectively while the other ends of these primaries are connected together forming the neutral 25. Neutral may be connected as by a lead 29 to the neutral of the main generator windings 2, 3 and 4.

In operation, the main windings 2, 3 and 1 of the generator 1 areadapted to supply electrical energyat the desired potential to the power bus 10, 11 and 12. The auxiliary indiugs 14:, 15 and 16 are designed'to produce electrical energy at a higher potential than that desired to be impressed upon the auxiliary power circuit 21, 22 and 2 The transformer bank 2 1 is used to lower the potential of the current delivered by the auxiliary windings so as to adapt the output of thesewindings for supplying the auxiliary power circuit. The current from the auxiliary windings 11-, 17 and 1G suffers a drop in potential in passing through the secondaries 17, 18 and 19 of the bucking transformer. The energy represented by this drop in potential is absorbed by the primaries 26, 27 and 28 or" the transformer bank 2 1 and is passed on to the main load circuit connected to the power bus 10, 11 and 1.2. Thus,

: durin normal 0 ieration of the enerator O C a certain proportion of the energy supplied by the auxiliary windings is passed on to the main load circuit while the remainder is used to supply the generator auxiliaries on the and 23. The voltage of the line 21, 22 and 23 maybe considerably lower than-that existing at the-terminals of the windings'l, 15 and 16 owing to the drop produced in the transformer banl 24a I In the event that a shortv circuit occurs on the main power bus 10, 11 and 12, the potential of this bus is reduced substantially LO-Z810 value and the M. F. at the terminals of the main windings is also reduced to a value dependingupon the characteristics of the generator 1 and that of the reactors 5, 6 and 7. The E. M. F. at the terminals of the auxiliary windings is proportionally reduced. During such period of short circuit there is no voltage on the transformer primaries 26, 27 and 28 and hence there is very little loss of voltage in the secondaries 17, 18 and 19, so that the voltage impressed upon the auxiliary circuit 21, 22 and 23 is substantially that existing at the terminals of the auxiliary windings. By suitably proportioning the windings of the generator 1 and the reactors 5, 6 and 7 the E. M. F. at the terminals of the auxiliary windings 14, 15 and 16 may be made to assume any desired value within reasonable limits during periods of short circuit of the bus 10, 11 and 12. By proportioning these parts so that under short circuit conditions the voltage at the terminals of the auxiliary windings is greater than the operating voltage of the auxiliary circuit by an amountequal to the impedance drop in the transformer 24:, then the auxiliary windings will maintain the desired operating voltage upon such auxiliary circuit even during periods of short circuit of the main bus. Thus, the auxiliaries of the generator 1 have a substantially constant source of power supply under all conditions from no load on the generator circuit to short circuit thereof.

In a typical installation of this character, the auxiliary windings 14:, 15 and 16 may be designed so as to normally generate a voltage twice as great as that required by the auxiliary motors on the line 21, 22 and 23. This aerated voltage may be graphically indi- ...ted by thelincs 31, 32 and 33 of Figure 2. Assuming this voltage to be for xample 4800 volts, then the same is bucked down by the windings 1T, 18 and 19 by the amounts illu trated at 3%, 35 and 36 of Figure 2 or 24 1!) volts. The voltage ZICI'HSF; the auxiliary circuit 21. and 251 is therefore 2400 volts. so that with full loadon the auxiliary windiugs, one halfthe total energy supplied by these windings is turned into the main load circuit through the bucking transformer bank and the other half is fed to the auxiliary c cuit. Should the generator he wound with .u each auxiliary winding will ially 14% of the generator which will be turned into the niaiu circuit and the remaining 7% supplied tcthe auxiliaries.

Under such assumptions, the rcactance voltagjge drop of the main machine windings as well as that of the reactors 5, 6 and 7 may be made to equal 15% of the terminal voltage oi the normal main machine winding at full load so that the total reactance drop to the main bus 10, 11, 12 is 30%. \Vith the main windings carmble of feeding 1.8 times normal sweat in o a three tim sh w a h ha then i sert f a sho t ais n the internal generated voltage or the main wi n S i b approx a ly 5 1 54% .0 normal and the voltage will be 27% of o m l- Since the au l ary Win ings have generated in them ,a voltage approximately equal in ercent to that generated in the main win gs, then the voltage so generated is 54% M74809 volts Or 2592 lt .Qw ng to the s o c rcu e e i no voltage on the primaries 2,6, 27 and 28 and h n en s ve yh fle l s l a in secondaries 17, 1,8 and 1?, with the result that the voltage .onthe auxiliary circuit 21, 2 2 and 23 is 2592'lcss the impedance drop in the generator and transformer windi Thus the v l age mpre s d 359 the auxlliary cir ui i subs ant a y volts r gardles of nditions in the nain load circuit which is high- 1y i esirable in power plants where continuous and reliable service is'essentia In Figure 3 the generator 1 is shown cona ct d thro gh hree pha e ans orme eels .3 to a transmis o line 3.9, 40 and 1- The main windings 3 and 4 of the generator are connected by loads 42, 43 and 44 to the rimaries 45, 46 and 47 of the transformer nk 38- The neut a P nt 48 of t priniaries 45, 46 and 47 may be connected as by a ea t th n ut al .3 o h ma n ge rator windings. The secondaries 50, 51 and 52 of the transformer 38 are connected directly to the transmission line 39, and 4 1. The

auxiliary windings 14, and16 of the generator 1 are connected to corresponding ends of tertiary windings 53, 54 and 55 respectively incorporated in the transformer rank 38. Tertiary windings 53, 54 and 55 act to normally buck the voltage of the auxiliary generator windings down to the value desired to be iinressed upon the auxiliary circuit 56,

' 5? an 58 that 18 connected to the other ends of these tertiary windings. This auxiliary circuit corresponds to auxiliary circuit 21, 22 and 23 of Figure 1 and is used to supply electrical energy to the auxiliaries of generator 1. In the event of a short circuit on the transmission line 39, and 41 the Volta V on the primary andsecondary windings of t e trans-.

as existed prior to the short circuit condi tion, provided the characteristics of the transformer bank are of the proper valuesto secure this result. For exam is, if the transformer bank 88 is designed to have impedance of 16% and ifthis irgtpedance is divided wet the Prui a y approximately egiually d t a y in? endthe twinne secondary windings, hen the tptai impodmance n t e c cui paladins th t o he wit se o ator ind ngs i 161 5 r 31% a idf i t e ene a r can s p y ,1- 8 offullload c rent throu h this impedance during short circuit oi the transmission line then the ine n l vo tag w l b -7 3 0r PP Ox mately The bucking voltage across tiary windings 53, Y54 and 55 will equal 1.78 X 8% =14% of ,full load Volta c a proximately. As the voltage generate in t e auxliary ad ng- ,5 and l i p g 4800 .55=2640 volts approximately and the amount of buck in the transformer windings is 2400 .14 or 340 volts then the auxiliary motors will receive 2640 r 340 2300 volts approximately, which is substantially the same as the 2400 volts which was-impressed on the line prior to the short circuit.

In the arrangement illustrated in Figure 3, the reactors 5, 6 and 7 are unnecessary lIlllS' much as the reactance of the transformer bank 38 is utilized to limit the short circuit current in the main windings.

It is obvious that this invention may be applied if desired to present standard generators of the type having but one winding conuected to a bus through reactors. In th s case two transformer banks maybe used, the first having its primaries connected between the generator and the reactors and the second having its primaries connected between the reactors and the bus, The secondariesof the second bank would be wound to have a lower voltage than the secondaries of the first bank and would be connected to buckdown the voltage of the first bank. The auxiliary to s would therefore receive a volta e equal approximately to the difference in M e induced voltage of the first and secondtransformer banks. trated inFigure 4 wherein the generator 60 is adapted to supply current to leads 9, 13 and 20 as in Figure 1. The auxiliary genen' ator windings are omitted however, and a transformer 61 has primaries 62, 6:3 .64 connected to leads 9, Band 20, which thusformer is adapted to energize auxiliary windings 14, 15 and 16. remainder of the diagram Figure 4 is omitted as the structure involved is identicalwith the corresponding portion of Figure 1, totheright of line a.a in said 1; l c

A any dm se cou d be'madein above construction and. many "a, pampty widely difierent embodiments of invention could be made -d4s art-i-ng the scope thereof, it n eud dt Such an arrangement is llusenergy, a main power circuit having an impedance in series relation with said source, an additional impedance connected through said series impedance to said source, an auxiliary power circuit connected to receive energy from said source, and means inductively connected to said additional impedance, said means acting to buck down the voltage of said auxiliary power circuit.

2. In an electric generating system, a power circuit, an auxiliary power circuit, transformer means associated with said power circuits, and a generator having a main winding and an auxiliary winding, said main winding being adapted to supply electrical energy to said first named circuit and said auxiliary winding being adapted to supply energy to said transformer means, said transformer means acting to furnish a part of the energy so received to saidfirst named clrcuit and the remainder to said auxiliary power circuit in such proportions, that regardless of voltage variations in said first named power circuit, the volta e of said auxiliary circuit remains substantially constant.

3. In an electric generating system, a power circuit, an auxiliary power circuit, bucking transformer means associated with said power circuits, and a generator having a main winding and an independent auxiliary winding, said main winding being adapted to supply electrical energy to said first named circuit and said auxiliary winding being adapted to supply energy through said bucking transformer means to said auxiliary power circuit, said transformer means acting to maintaina substantially constant voltage upon said auxiliary circuit by variations in its bucking action that are substantially proportional to voltage changes in said first named circuit.

4. In an electric generating system, a power circuit, an auxiliary power circuit, transformer means cooperating with said power circuits, and a generator having a main winding and an auxiliary winding, said main winding being adapted to feed its generated energy to said first named circuit and said auxiliary winding being adapted to feed 1ts generated energy to said auxiliary power circuit, said transformer means being adapted to feed a portion of the energy generated in said auxiliary winding into said first named circuit, the amount of power so fed by said transformer means being substantially proportional to the excess voltage generated in said auxiliary winding over that required by said auxiliary power circuit.

5. In an electric generating system, a main power circuit, an auxiliary power circuit, reactive means in series with said main power circuit, a generator having a main winding and an auxiliary winding, said main winding being adapted to feed its generated energy through said reactive means into said main power circuit, a bucking transformer adapted to be excited by current from said main winding with said reactive means intervening, and said auxiliary winding being adapted to feed said auxiliary. circuit, said reactive means cooperating with said bucking transformer to maintain a substantially constant voltage on said auxiliary circuit under varying load conditions on said main circuit.

6. In a generating system, a enerator having two windings, one of said windings being adapted to supply electrical energy to a load, an auxiliary power circuit supplied with electric energy from the other of said windings, and a bucking transformer excited by energy from said first named winding and acting to reduce the voltage supplied to said auxiliary power circuit.

7. In a generating system, a ower circuit, an auxiliary circuit and trans ormer means connected to said power circuit and to said auxiliary circuit, said transformer means acting to buck down the voltage of said auxiliary circuit at times of light load on said power circuit, both said power circuit and said transformer means being subject to concurrent and substantially equal voltage changes.

8. In combination, a source of electrical energy, a main load circuit connected to said source, impedances included in said main load circuit and connected in series relation with said source, an auxiliary power circuit connected to receive energy from said source, and transformer means having primary windings connected to said power source through said impedances and secondary windings connected in said auxiliary power circuit to buck down the voltage thereof.

9. In combination, a power circuit having a portion thereof subject to some variation in voltage with given variations in load and a second portion thereof subject to relatively great variations in voltage with said given variations in load, and an auxliary power circuit coupled to said first named portion of said power circuit to receive electric energy therefrom, said auxiliary power circuit being coupled to the second named portion of said power circuit to deliver a portion of its received energy thereto, such delivered energy being proportional to the voltage of the second named portion of said power circuit at the point of coupling of said auxiliary power circuit thereto. 7

10. In a generating system, a power source,

said power source being subject to some change in voltage with given variations in load thereon, a load circuit connected to said power source, said load circuit being subject to relatively great changes in voltage with said given variations in load, an auxiliary power circuit connected to said power source, and transformer means connected to said load circuit and to said auxiliary power circuit, said transformer means applying a va- 

